Volatile cyclic silicones which are disclosed in Japanese Patent Nos. 2517311, 2525193, 2843266, 2934773, 2967141, and 3020716 have been widely used in water-in-oil type emulsions and oil-based cosmetics.
Generally, human secretions such as sweat, tears and sebum cause makeup runs. Specially, in makeup cosmetics, an oil agent contained in cosmetics along with sebum secreted from the skin causes excessive wetting of cosmetic powder, which results in serious makeup runs. In order to reduce the amount of cosmetic oil remaining on the skin, an attempt was made to use a volatile oil such as octamethylcyclotetrasiloxane or decamethylcyclopentasiloxane as a part of the oil ingredients to be added.
Water is also an external factor causing poor coverage with cosmetics. In order to improve such poor makeup coverage caused by substances soluble in sweat or water, or to maintain a protective effect on the skin by preventing loss of water-soluble components from the skin, silicone oil was added to increase water repellency. Since silicone oil represented by dimethylpolysiloxane demonstrates superior features such as light to the touch, excellent water repellency, and high safety when applied, it has been used as an oil agent in cosmetics along with a volatile silicone.
However, since octamethylcyclotetrasiloxane which is a volatile silicone (hereinafter referred to as D4) has a solidification point of 17° C., D4 in a product containing D4 crystallizes in winter to cause separation in the product. In addition, when manufacturing such a product in winter, D4 must be dissolved once by heating prior to its addition, which is a source of concern in the manufacturing process.
Since decamethylcyclopentasiloxane (hereinafter referred to as D5) has a solidification point of −40° C., the above-mentioned problem does not occur. However, since its boiling point is so high as 210° C., it lacks volatility, so that there is a problem with sensory features if D4 is replaced with D5. Another problem therein is that as D5 remains on the skin for a longer time, strength of the cosmetic film is weaker, so that the duration of the cosmetic coverage is reduced. For this reason, D4 and D5 were mostly used together in practice to attain volatility and prevention of crystallization together.
On the other hand, as disclosed in Japanese Kokai (Laid-Open) Patent No. 9-175940, it is known to blend a solution of a silicone resin (trimethylsiloxysilicate) in D5 to sunscreen agents and cosmetic foundations. In this case, it is also known that the duration of the cosmetic coverage is improved on account of the addition of a silicone resin solution. However, the reality was that when the effect of a silicone resin solution was tested both in model experiments and in actual applications, the effect achieved in the actual applications was not so high as the effect achieved in the model experiments. The reason for this seems that D5 does not vaporize and remains on the skin, so that the effect of the silicone resin is not exhibited.